During the systematic studies of antitumor antibiotics, a novel antitumor antibiotic BMG 162-aF2, which was named spergualin, was found in a culture filtrate of a strain BMG 162-aF2 (FERM-P 5230; ATCC 31932) of Bacillus laterosporus belonging to the genus Bacillus [Umezawa et al., Journal of Antibiotics, Vol. 34, p. 1619 and p. 1622 (1981), and Umezawa et al., U.S. patent application No. 297,458 filed Aug. 28, 1981]. The chemical structure of spergualin is represented by the formula ##STR7## The configuration at the position 15 is S, while that at the position 11 is yet to be determined [Journal of Antibiotics, Vol. 34, 1622 (1981]. The compound of this formula is synthesized by the condensation of the acid amide and glyoxylylspermidine (Umezawa et al., U.S. patent application Nos. 375,916 and 375,950 filed May 5 and May 7, 1982, repsectively). The resulting epimeric compound is resolved into natural (-)-spergualin and non-natural (+)-spergualin [Journal of Antibiotics, Vol. 34, 1625 (1981)].